Numerous applications exist in which it is desired to form repeating patterns having a very short pitch. For instance, integrated circuit fabrication may involve formation of a repeating pattern of memory-storage units (i.e., NAND unit cells, dynamic random access [DRAM] unit cells, cross-point memory unit cells, etc.).
Integrated circuit fabrication may involve formation of a patterned mask over a semiconductor substrate, followed by transfer of a pattern from the mask into the substrate with one or more etches. The pattern imparted into the substrate may be utilized to form individual components of integrated circuitry.
The patterned mask may comprise photolithographically-patterned photoresist. Multiple separate photomasks (or reticles) may be utilized in photolithographically creating a desired masking pattern in photoresist. A problem that may occur is that each photomasking step introduces risks of mask misalignment. Another problem is that each photomasking step is another step in a fabrication process, which can increase costs and reduce throughput relative to fabrication processes having fewer steps.
A continuing goal of integrated circuit fabrication is to increase integrated circuit density, and accordingly to decrease the size of individual integrated circuit components. There is thus a continuing goal to form patterned masks having increasing densities of individual features. In cases in which the patterned masks comprise repeating patterns of features, there is a continuing goal to form the repeating patterns to higher density, or in other words to decreasing pitch. It would be desired to develop new methods of forming patterns which enable repeating patterns to be formed to high density.
There is also a continuing goal to reduce costs and increase throughput. It is thus desired to develop methods of forming patterns which enable repeating patterns to be formed with relatively few photomasking steps.